Isolating temperature sensitive components from heat sources in integrated circuits

ABSTRACT

Temperature sensitive devices may be shielded from temperature generating devices on the same integrated circuit by appropriately providing a trench that thermally isolates the heat generating devices from the temperature sensitive devices. In one embodiment, the trench may be formed by a back side etch completely through an integrated circuit wafer. The resulting trench may be filled with a thermally insulating material.

BACKGROUND

[0001] This invention relates generally to heat isolation in integratedcircuits.

[0002] In integrated circuits, a variety of components may be included.Some of these components may be high heat generators. Other componentsmay be relatively sensitive to either higher temperatures or variationsin temperatures.

[0003] In order to reduce costs, it may be desirable to integrate asmany different components in the same integrated circuit. Thisintegration not only reduces costs, but also reduces size. However,integrating more components makes it more likely that temperaturesensitive devices may be integrated with high heat generating devices.

[0004] Thus, there is a need for better ways to integrated differenttypes of devices into the same integrated circuit without creating heatrelated problems.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005]FIG. 1 is a bottom plan view of an integrated circuit inaccordance with one embodiment of the present invention; and

[0006]FIG. 2 is an enlarged cross-sectional view taken generally alongthe line 2-2 in FIG. 1 in accordance with one embodiment of the presentinvention.

DETAILED DESCRIPTION

[0007] Referring to FIG. 1, an integrated circuit 10 may include avariety of integrated components. For example, a circuit or devicesensitive to temperature variations may be located at the region 12 a. Aheat generating device or circuit such as a power amplifier may belocated at each of the regions 12 b and 12 c. Thus, it is desirable toisolate the region 12 a from both the regions 12 b and 12 c.

[0008] To this end, a filled, L-shaped trench 14 a may be arrangedaround the edges of the region 12 b. In this case, the two sides of therelatively rectangular region 12 b facing towards the region 12 a may beshielded by the filled, L-shaped trench 14 a. The region 12 c may beisolated by a completely encircling filled trench 14 b. The trenches 14are effective to isolate the heat generating circuit regions 12 b and 12c from the temperature sensitive circuit region 12 a.

[0009] Thus, as shown in FIG. 2, a region 12 c of the integrated circuitsubstrate 10 may have formed therein a heat generating circuit 20. Thecircuit 20 may be formed in and on the semiconductor substrate 11. Overthe substrate 11 may be a top side dielectric layer 16.

[0010] In one embodiment of the present invention, the trenches 14 maybe formed by a back side etch from the back side of the substrate 11while the circuit 10 is in the wafer form. The back side etch may usethe top side dielectric layer 16 as an etch stop. Thus, in oneembodiment of the present invention the back side etch may extendcompletely through the wafer substrate 11 to reach the etch stopdielectric layer 16 on the top side of the wafer.

[0011] Thereafter, the trenches 14 may be filled with a suitable fillmaterial 18 that has suitable heat insulating properties. For example,amorphous silicon dioxide may be utilized as a heat insulating fillmaterial 18. In some embodiments, no trench fill may be utilized. Inother embodiments, the trenches 14 may be formed from the top side ofthe wafer instead of the back side, using conventional isolation trenchtechnology.

[0012] As a result, detrimental high temperatures or temperaturefluctuations due to high power consuming devices, such as radiofrequency power amplifiers, may be reduced as seen by temperaturesensitive devices coexisting on the same integrated circuit 10.

[0013] While the present invention has been described with respect to alimited number of embodiments, those skilled in the art will appreciatenumerous modifications and variations therefrom. It is intended that theappended claims cover all such modifications and variations as fallwithin the true spirit and scope of this present invention.

What is claimed is:
 1. An integrated circuit comprising: a heatsensitive region; a heat generating region; and a trench arranged toshield the heat generating region from the heat sensitive region.
 2. Thecircuit of claim 1 wherein said trench is arranged around at least twosides of the heat generating region.
 3. The circuit of claim 1 whereinsaid trench completely encircles the heat generating region.
 4. Thecircuit of claim 1 formed on a semiconductor substrate, said trenchextending completely through said substrate.
 5. The circuit of claim 4including a dielectric layer on the upper surface of said substrate. 6.The circuit of claim 1 including a trench fill material in said trench.7. The circuit of claim 6 wherein said trench fill material is amorphoussilicon dioxide.
 8. The circuit of claim 1 wherein said circuit includesa semiconductor substrate and said trench extends into said substratefrom the back side of said substrate.
 9. The circuit of claim 8 whereinsaid trench extends from the back side of said substrate completelythrough said substrate.
 10. The circuit of claim 9 wherein said trenchis filled with a heat insulating fill material.
 11. A method comprising:forming a first circuit sensitive to heat in a first region of anintegrated circuit; forming a second circuit that generates heat in asecond region of an integrated circuit; and forming a trench around saidsecond region to shield the first circuit from the heat generated bysaid second circuit.
 12. The method of claim 11 including forming saidfirst and second regions on a semiconductor substrate and forming thetrench extending completely through said substrate.
 13. The method ofclaim 12 including forming a dielectric layer on said substrate andusing said dielectric layer as an etch stop.
 14. The method of claim 13including filling said trench with a trench fill material.
 15. Themethod of claim 14 including filling said trench with amorphous silicondioxide.
 16. The method of claim 1 including forming said trench using aback side etch.
 17. An integrated circuit comprising: a semiconductorsubstrate; a first region of said substrate including a first elementthat is sensitive to heat; a second region of said substrate including asecond element that generates heat; a trench arranged between said firstand second regions, said trench extending completely through saidsubstrate.
 18. The circuit of claim 17 wherein said substrate includes atop side and a back side and said trench extends from said back side tosaid top side.
 19. The circuit of claim 17 including a dielectric layerover said substrate and over said trench.
 20. The circuit of claim 17wherein said trench is filled with a trench fill material.